In the construction of naturally lit structures (e.g., greenhouses, pool enclosures, conservatories, stadiums, sunrooms, and so forth), glass has been employed in many applications as transparent structural elements, such as, windows, facings, and roofs. However, polymer sheeting is replacing glass in many applications due to several notable benefits.
One benefit of polymer sheeting is that it exhibits excellent impact resistance compared to glass. This in turn reduces maintenance costs in applications wherein occasional breakage caused by vandalism, hail, contraction/expansion, and so forth, is encountered. Another benefit of polymer sheeting is a significant reduction in weight compared to glass. This makes polymer sheeting easier to install than glass and reduces the load-bearing requirements of the structure on which they are installed.
In addition to these benefits, one of the most significant advantages of polymer sheeting is that it provides improved insulative properties compared to glass. This characteristic significantly affects the overall market acceptance of polymer sheeting as consumers desire a structural element with improved efficiency to reduce heating and/or cooling costs.
With current global warming issues, insulation properties of the polymer sheeting are getting more and more important. The trend is to go to higher gauges and multiple layers (e.g., five and more) with air channels in between the layers; all to create a lower U-value (insulation), to save on energy consumption, and thus result in less carbon dioxide (CO2) pollution.
During the production and scale up of these sheets with higher gauges, a processing problem was observed. The heat in the multiwall sheet cannot be sufficiently reduced and/or removed, in the calibrator zone of the extrusion process, resulting in the production of out of specification material with collapsed ribs and/or other issues.
Hence, there is a continuing need for multiwall sheets with reduced collapsed ribs and a process to produce the same.